.ao a, .quan a, .giay a, .tuisach a{
    float: left;
    margin-top: 20px;
    margin-left: 40px;
    text-align: center;
    text-decoration: none;
    color: blue;
}
.ao a:hover, .quan a:hover, .giay a:hover, .tuisach a:hover{
    color: red;
    text-decoration: underline;
}
